Control system for submersible motors and the like



DeC. 14,-1937 E. MENDENHALL ET AL. 2,102,013

CONTROL SYSTEM FOR SUBMERSIBLE MOTORS AND THE LIKE Filed Aug. 28, 1954 3 Sheets-Sheet l [NI/fNTOR6 EARL MENOENHALL L/UN/UJ 15. MIN ORN A TTORNEX Dec. 14, 1937. E. MENDENHALL ET AL. 2,102,018

CONTROL SYSTEM FOR SUBMERSJ IBLE MOTORS AND THE LIKE Filed Aug. 28, 1934 Sheets-Sheet 2 I .[NVf/VTORJ E, A 54m MENDE/VHALL 1 JUN/U6 5. l/A/VHORN Dec. 14, 1937. E. MENDENHALL ET AL. 2,102,018

CONTROL SYSTEM FOR SUBMERSIBLE MOTORS AND THE LIKE Filed Aug. 28, -l934 3 Sheets-Sheet 5 ATTORNEY.

Patented, Dec. 14, 1937 UNITED STATES PATENT OFFICE CONTROL SYSTEM FOR SUBMERSIBLE M- rons AND 'rnn LIKE Application August 28,

9 Claims.

Our invention relates to the art of controlling submersible electric motors and the like in 'response to the conditions existing therein, or for otherwise indicating the existence of such conditions, and consists in novel methods and apparatus foraccomplishing such ends.

In the preferred embodiment a shell is provided which contains an internal liquid, usually of dielectric character and having access through one means or another with a conducting liquid, usually the external liquid in which the shell is submerged. Excessive amounts of such conducting liquid should not be allowed to enter the shell, and it is an important object of the present invention to provide a system functioning in response to the relative amounts of the dielectric and conducting liquids in the shell, and to provide a novel method of controlling a structure such as a submersible motor, or otherwise indicating adverse conditions therein.

In one embodiment of the invention bodies of taminated by the conducting liquid, this action apparently taking place through a molecular interchange at the surface of contact. There are several ways of slowing up or preventing this contamination at the surface of contact, but should such means fail to function it is desirable to be able to control the structure so that no detrimental results will take place. In other instances the dielectric liquid may become contaminated through a defective sealing action. However, regardless of how this contamination takes place, the resulting condition is one in which the relative amounts of the two liquids in the shell is not correct, too much of the conducting liquid being present. It is an object of the present invention to provide a method and apparatus for indicating this condition to, the

operator, or to automatically control the system I 45' in response to such conditions.

In other instances the excessive amount of the conducting liquid in the shell may exist due to contraction or leakage of the dielectric liquid from the shell, thus allowing thebody of conducting liquid ,to increase in size proportionately. Further objects of the invention lie in the provision of a system which indicates such a condition to the operator or which controls the structure in accordance with such conditions.

When the invention is applied to a submersible 1934, Serial No. 741,796

electric motor, it is desirable to de-energize the motor should an excessive amount of the external liquid enter the motor shell, and it is an object of the present invention to provide such a method and apparatus.

Such a control system may conveniently include one or more electrodes extending in the dielectric liquid toward the surface of contact of the dielectric liquid and conducting liquid, these electrodes being included in one or more control circuits, and it is an object of the present invention to provide one or more of such control circuits which can be used either for indicating purposes or'control purposes.

In many systems wherein an electric means such as an electric motor is positioned inside a shell containing a dielectric liquid, the dielectric properties must be maintained to prevent electrical failure of the motor or other electric means. Even extremely minute and almost infinitesimal quantities of conducting liquid must be eliminated, and it is an object of the present invention to provide a novel structure responsive to extremely minute quantities of such a conducting liquid present in a dielectric liquid, and, in some instances, to use this structure for control or indicating purposes.

One form of such a structure which We have found particularly desirable includes a pair of conductor means spaced from each other in the dielectric liquid so that the current between these conductor means varies in response to the quantity of contaminating liquid present in the dielectric liquid. The provision of a novel form of such a structure is included among the obof novel form between which is positioned a mav terial having an amnity for the contaminated or conducting liquid. 7

This structure is so sensitive that difliculty is sometimes encountered due to the minute amount of moisture which condenses on the inner walls of the shell during or immediately after installation, this minute amount of moisture being suffi- A cient to actuate the control or indicating system.

amount of moisture is usually unobjectionable and, in fact, the dielectric liquid appears to increase in dielectric strength when the motor has been energized for a time. "If the structure is too sensitive its operation may be so critical that it is responsive to a temporary adverse condition which would be overcome upon continued operation of the motor or other electric means. overcome this difliculty we have provided an auxiliary circuit capable of drying out the structure or otherwise removing at least a portion of the contaminating liquid from the material having amnity therefor. If the adverse condition is not cleared up, the structure will later give another indication through increase in current. However, if the condition has'been corrected, no further indication will be given by this structure. It is an object of the present invention to provide a structure responsive to the amount of contaminating material in the dielectric liquid, and which includes these or equivalent features.

It is a further object of the invention to provide such a structure in which the sensitivity can be controlled.

Another object of the invention is to provide a system utilizing the conductors supplying current to the motor or other electric means for control purposes, andto provide such a system in which the unbalancing of any phase of a multiphase supply circuit is detected. and used for control or indicating purposes.

Other objects and advantages of the invention will be evident to those skilled in the art from the following description.

For purpose of illustration and definiteness the invention will be hereinafter described with reference to a submersible electric motor structure. It should be understood, however, that the principles herein disclosed can be used in other capacities or for controlling other means, or can be used in other types of installations regardless of whether or not these installations are submerged.

Referring to the drawings,

Fig.- 1 illustrates a submersible motor-pump unit installed in a well and incorporating certain of the control-devices of our invention.

Fig. 2 is a wiring diagram of the apparatus illustrated in Fig. 1.

Figs. 3, 4, and 5 are wiring diagrams of alternative forms of the invention.

Fig. 6 is a fragmentary view illustrating the' moisture-indicating structure.

Figs. 7 and 8 illustrate alternative forms of the through the opening 33. Due to the great differmoisture-indicating structure.

Fig. 9 is a wiring diagram of an alternative form of control system utilizing the structure shown in Fig. 8.

Referring particularly to Fig. 1, we have illustrated a well casing ll positioned in a well and filledwith water or other conducting liquid to a as indicated by the arrows l8, and discharging.

this liquid upward through the discharge pipe l5. A motor m'ririves the runners of the pump unit It through a shaft -2l.extending through a wall 22 of the motor shell l1, this shaft being sealed relative to this wall by "a suitable sealing device'23.

This sealing device is preferably of the mercury-* sealed type, but could be replaced by any seal which effectively prevents water from entering the motor shell I! at thejunction of the shaft 2| and the wall 22. The motor is positioned in a motor chamber 24 of the motor shell I! and comprises the usual stator 25 and rotor 26, the latter being journalled in suitable bearings, such as those illustrated.

A balance or expansion-permitting chamber is formed in the lower end of themotor shell H,-

the upper end of this chamber being defined by a baflie 3| extending thereacross. This baflle includes one or more openings 32 which communicate between the motor c amber 24 and the upper end of the balance chamber 30. The lower end of this balance chamber is in open communication with the external liquid in the well through an opening 33 or other equivalent means.

In open communication with the interior of the motor shell I I, and thus in open communication with the motor chamber 24 and the upper end of the balance chamber 30 is a pipe 35 which extends upward to the surface of the ground, this pipe carrying the conductors supplying the current to the motor and also the control conductors to be hereinafter described, these conductors being of such diameter as to not completely fill the pipe 35 so that the space around these conductors is open.

The upper end of the balance chamber and the motor chamber 24 contain a dielectric liquid such as dry oil. The balance chamber 30 thus contains pressure-equalized bodies of the dielectric liquid and the external or conducting liquid, these bodies being incontact at a surface 31. Due to the equalization of pressures between the dielectric liquid and the external or conducting liquid,

the dielectric liquid extends in the pipe 35 to a level 39. The'level 33 is usually slightly higher than the level l2 due to a difference in density between the dielectric liquid and the external or conducting liquid, the former being usually of less density than the latter.

,This system is veryadvantageous for it forms a dynamic system wherein the internal and external pressures on the shell I1 are always maintained substantially equal regardless of the position of the level l2. Thus, when the pump unit It is put into operation the level l2 drops, thus lowering the pressure on the external or conducting liquid in the balance chamber 30, and thus correspondingly lowering the level 39 of the dielectric liquid in the pipe 35. A corresponding amount of external or conducting liquid is forced ence in effective diameter between the balance chamber 30 and the pipe 35, the level 39 can change over wide limits, the corresponding movement of the surface 31 in the balance chamber being slight. v If, however, any contraction or leakage of dielectric liquid from the motor chamber takes place, or; if a sufficient amount of dielectric liquid is not supplied to the motor chamber in the first place, it is possible that the surface 31 may rise to such a point as to allow the external or conducting liquid to pass through the opening 32 and thus eventually into contact with the windings of the motor 20. This would, of course, shortcircuit these windings and necessitate the renewal thereof after the motor pump unit had been removed from the well. It thus becomes desirable to provide'means responsive to the relative .quantities of thetwo liquids inthe motor shell and either indicating the adverse condition or remedying it.

The surface 31 may, of course, be lowered at any time by pouring an additional supply of dielectric liquid into the upper end of the pipe 35, this additional supply forcing the surface 3'! downward and at the same time maintaining the equalization of pressures in the system. It is, however, desirable that this supply of dielectric liquid be accomplished automatically, and in Figs. 1 and 2 we have shown a system wherein this may be accomplished. In accomplishing this result it is necessary to provide some means operating as a function of the relative amounts of the two liquids in the motor shell I1, and in Figs. 1 and 2 we have illustrated this means as comprising an electrode) extending downward through an insulator from the baffle 3|. A conductor 4| is connected to this electrode and extends upward to the surface of the ground through the pipe 35, being connected to one terminal of a solenoid 42 associated with a magnetic valve 43, the other terminal of this solenoid being connected by a conductor 44 to a conductor 45 of athree-phase supply line including conductors 45 and 41, the lastnamed conductor being grounded as indicated by the numeral 48. When the surface 31' comes in contact with the electrode 49 a circuit is thus completed from the conductor 41 through ground, through the body of external or conducting liquid in the balance chamber, and through the electrode 40, conductor 4|, the solenoid 42, and the conductor 44. the solenoid and opens the valve 43 to allow dielectric liquid to move downward in the pipe 35 from a supply tank 49. This supply of dielectric liquid continues until the surface 31 is lowered from the electrode 40 at which time the circuit through the solenoid 42 is broken and the valve 43 again closes. i

In the event that the supply tank 49 should be dry, or in the event that the valve 43 did not function, it would be desirable to lower the surface 3'! by other means. we position a second-electrode 50 in the balance chamber and connect this second electrode to a conductor which extends upward and is connected to one terminal of a solenoid 52 of a magnetic valve 53, the other terminal being connected to the conductor 44, as shown in Fig. 2. The valve 53 may control the supply of air or other liquid or gaseous medium from a storage means 55 to the pipe 35.- Thus, if the surface 31 comes into contact with the electrode 59, a circuit is completed from the conductor 41 through the body of external or conducting liquid in the balance chamber and through the electrode 50, conductor 5|, solenoid 52, and conductor 44, thereby opening the magnetic valve 53, and allowing compressed air or other medium from the storage means 55 to be introduced into the pipe 35. This forces the level of, the dielectric medium in the pipe 35 downward but as soon as the surface 31 breaks contact with the electrode 50, the valve 53 closes.

If the pipe 35 is in open communication with the atmosphere, the rise or drop in the level, 39 will be approximately proportional to the rise or drop'of the level I2 of the external liquid, other factors being equal. ,Such communication to the atmosphere may beeifected at a position adjacent a pothead 56 oran open pipe 51 may be utilized extending to aipoint above the storage means 49 or 55. With such a system the storage means 49 may be ventedf to the atmosphere or may be closed. If'& gas supply is used with such a system, as distinct from a liquidsupply from This energizes- To accomplish this end the storage means 55, the upper end of the pipe 51 may include a valve 58 forming a restricted passage to allow pressure to be built up in the pipe 35 when gas is supplied thereto, a portion of this gas escaping upward through the restricted passage and thus giving an indication of the condition of the structure. Such a restricted passage will still permit open communication between the pipe 35 and the atmosphere to permit compensation in the amount of air in this pipe upon the slower shift in conditions effected by a change in the level I2. In other instances the pipe 35 can be closed from the atmosphere by eliminating the pipe 51 or closing the valve 58 and having the pothead 56 closing the pipe 35. In this instance the air in the pipe 35 will be slightly compressed or rarefied with change in the level 39. Oil or other liquid under pressure may be then used in the supply means 49 or 55 or both, these supply means being closed from the atmosphere.

Should the level 31 continue to rise, however, due to a failure of both the supply means, it is desirable to automatically de-energize the motor. This is accomplished by an electrode 50 extending into the balance chamber a distance less than the electrodes 40 and 50. A conductor 6| is connected to the electrode and extends through a structure responsive to the amount of external or conducting liquid contaminating the dielectric liquid, this structure being hereinafter termed a moisture-indicating relay 62 for definiteness. This relay 62 is positioned in the motor chamber preferably adjacent the stator winding and the current flowing through the conductor 6| thereafter flows upward to the surface of the ground to one terminal of a solenoid 63, the other ter minal thereof being connected to the conductor 45. The solenoid 63 may operate any control or indicating device, but is shown as being associated with a relay providing contacts 65 which form a part of a holding circuit for a main switch 66, this holding circuit also including a holding coil or solenoid 61 of the usual construction, this holding circuit being of a conventional type whereby energization of the solenoid 61 closes and maintains closed the main switch 66, thus supplying current from the conductors 45, 46, and 41 to intermediate conductors 10, H, and 12 extending downward through the pipe 35 and being connected to the stator winding.

In Fig. 2 we have shown one type of holding circuit including a starting switch 13, one terminal of which is connected to the conductor 45, and the other terminal of which is connected to an auxiliary switch 14 and to one of the relay contacts 65. Closing the switch 73 sends current from the conductor 45 through these relay contacts and through the solenoid 67 to the conductor 46, thus closing the main switch 66. As soon as this switch is closed the auxiliary switch 14 likewise closes and when the starting switch 13 is opened the holding circuit of the switch is maintained by current passing through the main switch and through the auxiliary switch from the conductor l0, the current returning to the conductor 46 through the relay contacts 55 and the holding coil 61, .as previously described. Should the level 31 come into contactv with the electrode 50 a circuit will be completed from the conductor 4'! through the body of external liquid in the balance chamber and through this electrode, the conductor 6|, and the solenoid "53, to the conductor 45. This energizes the solenoid 53 and opens the relay contacts 55. This le-energizes the holding circuit of the main switch 55 and allows this switch to move into open position shown in Fig.2.

In addition, however, ,it is sometimes desirable to close an alarm circuit I6 including a bell I1 or other indicating means when this condition occurs, and in accomplishing this end we utilize contacts 18 on the relay, which contacts are closed when the solenoid 63 is'energized: thus completing a circuit from the conductor 45 through the contacts 18 and through the circuit 16 and the bell H, the current returning to the conductor 46. The attention of the operator is at once called to this condition, and should he attempt to start the motor by closing the starting switch 13, no harm will result in view of the fact that the holding circuit of the switch cannot be closed due to the relay opening the contacts 65.

The moisture-indicating relay 62 is also a means responsive to the relative amounts of said dielectricJiquid and external or conducting liquid in the motor shell ll, this relay being responsive primarily to the, amount oi the contaminating liquid which has become associated with the dielectric liquid. It will also function should the surface 31 rise to this-relay. Suchcontamination may take place through several factors such as leakage of conducting liquid through imperfections in the motor shell or leakage through the seal 23, especially if certain types of seals are utilized. In addition, under unfavorable conditions there may be a slight contamination of the dielectric liquid at the surface 31], especially if portions of the interior of,the shell ii are not heatedas by the presence of the motor fill or other means.

The dielectric liquid is continuously circulated by the rotation of the rotor 26 or by other means, being moved through circulation paths such as indicated by the arrows We of Fig. 1, this being desirable in view of thecooling action exerted on the motor or other electric means. While this circulation is very desirable in this regard, it also serves to distribute any contaminating particles throughout the shell ll. It thus becomes desirable to know the condition of the dielectric liquid and the relative amounts of the two liquids in the material beingclrculated. The moistureindicating relay- 62 may be used in this capacity, being preferably positioned in the path ot'the circulating liquid and near the motor winding.

This relay 62 is of very'simple construction and may be formed in a mannerindicated in Fig. 6

by utilizing two cotton-covered conductor means twisted together so that the cotton insulation is positioned between the conductor means. The cotton covering on these conductor means has an affinity for any of the conducting liquid present in the dielectric liquid. In this embodiment there is impressed between the conductor means a potential, so that when the cotton covering at- ,tracts the conducting liquid which may be present in thedielectric liquid/the resistance between the conductors is decreased, thus changing the current flowing through any control circuit or any indicating circuit which may be connected to the moisture-indicating relay 62. In the embodiment shown one of the conductor means of this relay may be connected in series with the intermediate v portion of the conductor GI 50 as to form a part thereof, while one end of the other conductor means is grounded to some portion of the motor shell ll, the other end of this othervconductor means being electrically unconnected. With this form of connection the potential between the conbe operated and the switch 66 opened, as previously described. The motor cannot again beenergized until the adverse condition is corrected. as by supplying additional dielectric medium to the pipe 35 in suflicient quantities to replace or dilute the existing contaminated dielectric liquid, and until the moisture content of the cottoncovered insulation is decreased. This decrease in moisture content is in some instances automatically efiected due to the heating action between the two conductor means of the moistureindicatlng relay 62. In other instances it is necessary to force an auxiliary current therethrough to eiiect this drying action, or in extreme instances to remove the motor-pump unit from the well. It is not, however, necessary that we use cotton as an insulating medium, though this type of relay has been found to be both cheap and very efiective in practice. Other types of insulating media may be utilized, whether or not the particular medium used has a selective aty for the conducting liquid.

If the motor pump is not used for long periods of time, it is conceivable that the dielectric lin uid may become contaminated with the external or conducting liquid to such an extent that to start the motor would be detrimental. The moleture-indicating relay 52 will ordinarily take care of such a situation, but in the event that such a relay .is not used or in the event thatit becomes temporarily inoperative, we prefer to utilize an auxiliary relay 83. providing a solenoid winding dd connected between the conductors .66 and M and thus around the main switch E36. -lihis relay L iprovides contacts $36 which are closed when the solenoidyzinding an is energized, thus closing an alarm circuit i371 including a hell or other alarm means iid Assuming that the dielectric liquid becomes contaminated around the motor windings, it will at once be apparent that current will flow from the switch it through the. solenoid winding 86 and through" the conductor iii to the motor winding. If the amount of contamination has become sufiicient to carry a minute amount of current from any phase of the motor winding to ground, current will flow through the conductor ii and'will return through the grounded motor shell ill to the, conductor Gil, thus energizing the solenoid winding 84 and closing the alarm circuit.

In Fig. 3 we have shown the solenoid winding 86 of the auxiliary relay 83 as being associated with the relay in the holding circuit of the switch 66 so that energization of, the solenoid winding 86 will make it impossible to start the motor even thongh the starting switch i3 is depr in I accomplishing this end the pallet of the relay inthe holding circuit has an extension 90 on which a magnetic core 9| is positioned, this core being raised by the solenoid 84 when energized. A magnetic core 92 is acted upon by the solenoid 63. Both the solenoid 63 and the solenoid 84 tend, when energized, to raise the plunger of the relay, thereby opening the holding circuit. By this means it becomes impossible to start the motor if the relay in the circuit opens the contact 65 either because the surface 31 is raised to contact the electrode 60 or because a circuit has been completed through the solenoid 84 due to current passing from the winding of the motor to the grounded shell, as previously described. Thus, the system shown in Fig. 3 eliminates the use of an auxiliary alarm circuit 81.

, In Fig. 4 we have shown still another system which is simpler than the system shown in Fig. 2. In this system only a single electrode need be used, this electrode being indicated by the numeral I and being connected to a conductor I0I which may in turn be connected to a moisture-indicating relay, as previously described. The conductor IOI also conducts current to a solenoid winding I02 of a magnetic valve I03 controlling the flow from a supply tank I04 in a manner previously described. The solenoid I02 is also-connected through a conductor I05 to one terminal of a solenoid I01, the other terminal being connected by a conductor I08 to the conductor 45 of the supply line.

In this form of the invention, when the surface 31 comes into contact with the electrode I00, the solenoids I02 and I01 are simultaneouslyenergized'and remain energized until the surface 31 moves out of contact with the electrode I00. The energizing of the solenoid I02 opens the valve I03 and allows dielectric liquid or other material to be supplied through the pipe 35, as previously described. The energization of the solenoid I01 exerts aforce on a plunger H0 in a rightward direction, this movement being opposed by the action of a dashpot III which may be of any desired construction. So long as the solenoid I01 remains energized, however, the plunger IIO moves slowly to the right and after a predetermined length of time, a pallet II2 on the plunger IIO bridges across contacts II3, thus completing a circuit from the conductor 45 through the solenoid 63 of the relay associated with the holding circuit, the current returning to the conductor 46 of the supply line. This, of course, opens the main switch and deeenergizes the motor.

In the form of the invention shown in Fig. 4, if the dielectric liquid supplied through the pipe 35 does not lower the surface 31 within. a predetermined time, the time-limit relay will deenergize the motor. If subsequently the level 31 is lowered from the electrode I00, the motor will not automatically start in view of the fact that the main switch is open and current cannot thus flow through the auxiliary switch 14 and the holding circuit of this switch; The sys-.

tem can, however, be set into operation by closing the starting switch 13 in the usual manner.

The time-limit relay disclosed in Fig. 4 is, of course, diagrammatic and other forms of timeoperated switches may be utilized.

In Fig. 5 we have illustrated a system wherein no auxiliary control wires are. necessary, the only wires extending through the pipe 35 being the conductors 10, H, and 12. In this form of the invention we provide an electrode I20 connected conductor 41 through the body of external liquid in the balance chamber and through the electrode I and the conductor I 2I.

Any relay system may be utilized for determining when such an unbalanced condition exists. In Fig. 5 we have shown one system, indicating the current transformers associated with the conductors 10, H, and 12 by the numerals I30, I3I, and I 32 respectively. These current transformers are connected to solenoids I 35, I36, and I31 respectively, which are disposed 120 apart, the inner faces of which are spaced from each other as diagrammatically shown in Fig. 5. Extending between these inner faces is an armature I40 which has been shown as being triangular in shape. As shown to the left in Fig. 5, this tri angle-shaped armature I40 is connected to a ball I H journalled in a socket I42. Extending from this ball is a support I43 which normally engages the lower end of a plunger I 44 of an auxiliary relay I45 including contacts. I46 forming a part of the holding circuit of the main switch. The' contacts I46 are normally closed by a pallet I41 associated with the plunger I44, but if the support I43 is moved to one side, as indicated bythe dotted line I48, the plunger I44 will drop, thus breaking the holding circuit of the switch 66. Such a movement of the support I43 takes place when the triangle-shaped armature I40 is moved from its central position with relation to the solenoids I35, I36, and I31. Normally, when the three phases of the system are balanced the armature I40 will be spaced equally from each of the solenoids. If, however, the current through the conductor 10 becomes greater than the current through the conductors H or 12, for instance. the solenoid I35 will exert a greater pull on the armature I40 and will draw this armature toward the core of this solenoid, thereby moving the support I43 into its dotted line position I48 and thereby allowing the plunger I44 to drop to de-energize the holding circuit. This at once de-energizes the motor and the motor cannot be again energized until the auxiliary relay I45 is manually reset.

In other instances alternative forms of the moisture-indicating relay 62 can be used in conjunction with any of the systems hereinbefore described. It has been found that the type of moisture-indicating relay illustrated in Fig. 6 is extremely sensitive. Sensitivity is, of course, es-

sential, for we have found that one part of conducting liquid in ten thousand parts of the dielectric liquid will produce sufficient contamination to detrimentally affect and in some instances burn out the motor or other electric means. However, the moisture-indicating relay shown '11 Fig. 6 is responsive to much smaller quantities of the contaminating liquid. Experiments have shown that when a submersible electric motor, for instance, is first installed, the dielectric strength of the dielectric liquid will decrease until the motor has been operated for a period of time,.after which the dielectric strength again increases and in some instances becomes even quent increase in dielectric strength is no doubt due to the purifying action of the heat generated when the motor or other electric means is operating, together with the circulation system shown. The maintenance of differential temperatures in different portions of the motor shell appears to be a factorin this regard,- especially as to preventing contamination adjacent the surface 31, this contamination being apparently efiected through a molecular interchange at the surface of contact. With the type of moistureindicating relay shown in Fig. 6, the preliminary or temporary decrease in dielectric strength is often sufflcient to operate this extremely sensitive device, thus giving an indicationof a condition which would automatically correct itself should the motor continue to operate. It thus becomes desirable in some instancesto use a less sensitive moisture-indicating. device. Such alternative devices are illustrated in Figs. '1, 8, and 9.

Referring particularly to Fig. '1, a moistureindicating relay is shown as including a pair of conductor means I10 and I 1| each formed of a metallic plate preferably perforated as shown. Positioned between" these conductor means is a member I12, which, if desired, may be made of a substance having an amnity for the contaminating liquid. In this connection we find it very satisfactory to use a strip of fiber in this regard. different fibers producing different sensitivities. One of these conductor means may be grounded as indicated by the numeral I13 andthe other may be connected to a conductor Ill corresponding to the conductor SI of Fig. 2. If desired, an electrode may be used and connected to the conductor H to perform the functions previously set forth.

Another form of moisture-indicating relay which isoften desirable is illustrated in Fig. 8. Here two conductor means I80 and I8I are utilized. The conductor means I80 is formed of a metallic plate or'rod, preferably perforated as shown. The conductor means I8I may take the form of a coil of resistance wire disposed around the conductor means I80. Members I82 and I83 are positioned on opposite sides of the conductor means I and separate this conductor means from the coil of resistance wire. These members I82 and I83 may be formed of a material having an affinity for the contaminating liquid, fiber being very satisfactory in this regard, although other substances can be used.

Fig. 9 illustrates one mode ,ofconnecting the moisture-indicating relay shown in Fig. 8. A

conductor I corresponding to the conductor M I of Fig. 2 is electrically connected to the conductor means I80, and may also be connected to the electrode 80. One terminal of the coil of resistance wire I8I is grounded as indicated by the numeral I88, the other terminal being connected to a conductor I81 which extends upward in circult with the secondary'winding of the transformer I80 one terminal of which is'grounded as indicated by the numeral ,1 9 I there being a switch I92 in this circuit. The primary winding of the transformer I is connected between the conductors 66 and '41. The switch I82 is normally open during the operation of the atructiue. Even when the dielectric strength of the dielectric liquid is entirely satisfactory a minute current will flow from the conductor 41 through ground, through the conductor I86, and thence through the members I82 and I83 to the'cond'uctor means the solenoid winding 63. .This current will not, however, be sumcient to open the holding circuit 0 of the switch 66. Should the dielectric liquid become contaminated, the current through this circuit will increase in sufiicient quantity to open the switch 68.

It is desirable to be able to ascertain whether or not this adverse condition is only a temporary one which would automatically clear up the switch I 92. This auxiliary or heating circuit,

delivers suflicient current to the coil of resistance wire to locally heat the moisture-indicating relay suflicieiitly to drive out at least a portion of the conducting liquid which] may have become associated with the members I 82 or I83. It is not essential to actually vaporize this conducting liq-. uid, though this can be done if desired. Usually it is suflicient to pass a small current through the coil of resistance wire to produce a localized increase in temperature sufiicient to expel a portion of the conducting liquid which has become associated with these members I82 and I83. Thereafter the switch 66 can be again closed and the motor set into operation. If further operation of the motor does not alleviate the adverse condition the moisture-indicating relay will again operate, thusindicating that additional dielectric liquid should be supplied or that other means should be used to correctthe difficulty. If, however, the motor continues to operate without being de-energized by the moisture-indicating relay, it is a. clear indication that the adverse condition was only temporary. Should an excessive amount of the conducting liquid again become associated with the dielectric liquid, the mosture-indicating relay will, of course, operate to de-energize the motor.

While in Fig. 9 we have shown only two control conductors I85 and I81 extending upward to the top of the well, it will be clear that the conductor I85 serves adual purpose in conducting current either from the electrode 60 or the moisture-indica ting device. It is thus sometimes desirable to use two separate conductors in place of the single conductor I85, one extending upward from the electrode 8j0'and the other from the conductor means I80 of the moisture-indicating relay. Such conductors may be .used for separate control or indicating purposes, but preferably are both connected to the relay 82 for de-energizing the motor. 7

It should be clearly understood that the moisture-indicating relay can be used for purposes of indication as well as direct control. In this connection the pallet switch operated by the solenoid winding 83 can be visually observed, or any other suitable indicating means can'glbe connected in circuit with the moisture-indicating relay. It should also be clear that 'variousfeatures of the invention can be used individually-J Thus, it is 7 I80 of the moisture-indicating relay, returning to the conductor 45 through the conductor I85 and not always essential that a system beprovided material dispersed in the dielectric liquid.

which will supply both dielectric oil or air or other medium to the motor. In many installations we install only the means for supplying additional dielectric liquid to the motor. In still other installations it is possible to dispense with this means for supplying dielectric liquid, and utilize only the electrode 60 for de-energizing the motor or for indicating the presence of an adverse condition. In some instances even this electrode can be dispensed with and the moisture-indicating relay utilized to indicate an undesirable increase in relative amounts of the liquids in the motor shell, either through a rise in level of the surface 31 so that the conductor means of the moistureindicating relay are short-circuited, or by the presence of excessive amounts of contaminated In other instances it is possible to utilize only one or more electrodes 40, 50, or 60 for control or indicating purposes regardless of the presence of the moisture-indicating relay 62. In'this connection any of these electrodes, in effect, act in a manner somewhat analogous to the moisture-indicating relay if through molecular interchange at the surface 31, the material between this surface and the electrode becomes contaminated with conducting liquid in sufilcient degree to permit a current flow between the surface 31 and this electrode even though the surface31 does not directly contact the electrode. In this instance the electrode corresponds to one of the conductor means of the moisture-indicating relay. while the body of conducting liquid corresponds to the other conductor means. Such a system is not, however, as sensitive as the moisture-indicating relay shown. in Figs. 6, 7, or 8.

It will be understood that the particular apparatus illustrated has beenshown only diagram-' matically, and that many modifications in the apparatus, as-well as in the circuits utilized can be made without departing from the spirit of this invention. Thus, more sensitive relays or other amplifying devices can be incorporated in the control circuits in addition to the apparatus shown. So also, if local regulations prevent the grounding of one of the supply conductors, the potentials utilized for control or indicating purposes can be obtained from auxiliary sources, such as batteries or transformers. one terminal of which can be grounded if desired.

The present application is a continuation-inpart of our co-pending application Serial No. 524,494 filed March 23, 1931, now .Patent No.

We claim as our invention: I

1. In combination: a shell containing a dielectric liquid and having access to a conducting liquid tending to contaminate said dielectric liquid; circuit means extending from said shell; relay means in said dielectric liquid responsive to the-amount of said conducting liquid associated therewith and electrically connected to said cir-- cuit means to change the current flowing through said circuit means in response to the amount of said conducting liquid contaminating said dielectric liquid, said relay means including means having an aillnity for saidconducting liquid; means for heating said relay means for driving from said means havingan aflinity for said conducting liquid at least a part of the conducting liquid associated therewith; and means exterior of said shell and operatively connected to saidcircuit means to be responsive to current flowing through said circuit means.

2. In combination in a submersible structure: a shell containing a dielectric liquid and having access to a conducting liquid tending to contaminate said dielectric liquid; a control means for said submersible structure; a control circuit operatively connected to said control means; a pair of conductor means spaced from each other in said dielectric liquid and connected in said' control circuit whereby the current flowing in said control circuit changes in response to the amount of said conducting liquid contaminating that portion of said dielectric liquid adjacent said pair of conductor means; and an auxiliary circuit for sending current through one of said conductor means in sufficient quantity to heat same. 7

1.3. A combination as defined in claim 2 including means intermediate said spaced conductor means and having an aflinity for said conducting liquid, said auxiliary circuit heating this means to drive off at least a portion of the conducting liquid associated therewith.

4. In combination: a shell containing a dielectric liquid and having access to a conducting liq uid tending to contaminate said dielectric liquid; a pair of conductor means in said dielectric liquid ingliquid tending to contaminate said dielectric liquid; a. pair of'conductor means in said dielectric liquid and spaced from each other, one of said conductor means comprising a heating element; circuit means connected to said pair of conductor means; control means responsive to the current flowing in said circuit means; and means for heating said heating element to decrease the. amount of said conducting liquid. in the dielectric liquid between said conductor means.

6. A combination as defined in claim 4 including a body of material having an affinity for said conducting liquid and positioned between said conductor means.

7. A combination as defined in claim 4 in which both of said conductor means comprise interstitial structures and including a body of material having an aflinity 'for' said conducting liquid and positioned between said perforated plates.

- conducting liquid associated with a portion of said dielectric aliquid; means in said shell acting to purify said dielectric liquid. by removing the conducting liquid therefrom; and means for removing saidconducting liquid from said portion of said dielectric liquid at a rate faster than saicLme'ans in said shell will effect purification of the dielectric liquid in said shell.

9. A combination as defined in claim 2 in which one of said conductor means includes a. central conducting element and in which the other of saidconductor means includes a coilof wire 

